Abstract: The electrophilic substitution reaction occurring to the chelate ring of the complexes could be regarded as an indication of quasi-aromaticity of the ring systems, no catalyst was used and only triethylamine was employed, implying that the aroylating agents with different p-substituents are polarized enough to be effective electrophiles to attack the methine carbon of the electron-rich substrate 1. This property is probably the clue to polarization of the ligand electrons by the nickel(Ⅱ) ion and to the participation of the nickel(Ⅱ) in the π-bond systems of the two coordinated conjugated rings. The linearity relationship between vd-d maxima, E_1/2OX(1) and σ_p are obtained, respectively. The electronic environment of central metal ion as well as the aromaticity of the ring system are affected by the electronic properties of the p-substituents. A comparison of the electrochemical results with each other showed .that when the electronegativity of the substituent was higher, the oxidation(Ni²⁺/Ni³⁺) becomes more difficult.

Key words: Electrophilic substitution, Quasi-aromatic metal ions, Complex